<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../vue.js"></script>
</head>

<body>
    <div class="app">
        <h2 @click="say">{{sayHello}}</h2>
    </div>
    <script>
        const vm = new Vue({
            data: {
                sayHello: '点击同学你好'
            },
            methods: {
                say() {
                    // Vue.set(this, 'sayHello', '你好同学')
                    this.$set(this, 'sayHello', '你好同学')
                }
            }
        })
        vm.$mount('.app')
    </script>
</body>

</html>